Model of global spontaneous activity and local structured activity during delay periods in the cerebral cortex.

Journal Article (Journal Article)

We investigate self-sustaining stable states (attractors) in networks of integrate-and-fire neurons. First, we study the stability of spontaneous activity in an unstructured network. It is shown that the stochastic background activity, of 1-5 spikes/s, is unstable if all neurons are excitatory. On the other hand, spontaneous activity becomes self-stabilizing in presence of local inhibition, given reasonable values of the parameters of the network. Second, in a network sustaining physiological spontaneous rates, we study the effect of learning in a local module, expressed in synaptic modifications in specific populations of synapses. We find that if the average synaptic potentiation (LTP) is too low, no stimulus specific activity manifests itself in the delay period. Instead, following the presentation and removal of any stimulus there is, in the local module, a delay activity in which all neurons selective (responding visually) to any of the stimuli presented for learning have rates which gradually increase with the amplitude of synaptic potentiation. When the average LTP increases beyond a critical value, specific local attractors (stable states) appear abruptly against the background of the global uniform spontaneous attractor. In this case the local module has two available types of collective delay activity: if the stimulus is unfamiliar, the activity is spontaneous; if it is similar to a learned stimulus, delay activity is selective. These new attractors reflect the synaptic structure developed during learning. In each of them a small population of neurons have elevated rates, which depend on the strength of LTP. The remaining neurons of the module have their activity at spontaneous rates. The predictions made in this paper could be checked by single unit recordings in delayed response experiments.

Full Text

Duke Authors

Cited Authors

  • Amit, DJ; Brunel, N

Published Date

  • April 1997

Published In

Volume / Issue

  • 7 / 3

Start / End Page

  • 237 - 252

PubMed ID

  • 9143444

International Standard Serial Number (ISSN)

  • 1047-3211

Digital Object Identifier (DOI)

  • 10.1093/cercor/7.3.237


  • eng

Conference Location

  • United States